Method of controlling an automatic sheet feeder using multiple pulses

ABSTRACT

The operation of an automatic sheet feeder provided with a plurality of sheet hoppers which are used selectively to feed sheets to a printer is controlled. A control unit of the printer supplies a multiplex control signal including a hopper select signal and a sheet delivery signal to the automatic sheet feeder through a single signal line. The width of pulses of the hopper select signal is smaller than a predetermined time, while the width of the sheet delivery signal is greater than the predetermiend time. The pulses of the multiplex control signal are compared with the predetermined time to discriminate the hopper select signal and the sheet delivery signal from each other. That sheet hopper corresponding to the number of pulses of the hopper select signal is selected, and then the automatic feeding of sheets from the selected sheet hopper commences upon the reception of the sheet delivery signal.

BACKGROUND OF THE INVENTION

The present invention relates to a method of controlling an automaticsheet feeder installed on an impact printer and, more particularly, to amethod of controlling an automatic sheet feeder having a plurality ofsheet hoppers to change feeding from the sheet hoppers automatically.

An automatic sheet feeder installed on an impact printer feeds sheetsone at a time to the impact printer. When changing sheets having onewidth for sheets having a different width on such an automatic sheetfeeder, the positions of sheet guides provided on a sheet hopper must beadjusted according to the width of the sheets. A recently developedautomatic sheet feeder is provided with a plurality of sheet hoppersrespectively containing sheets of different widths to feed selectedsheets from the sheet hoppers.

FIG. 6 is a time chart showing the operation of an automatic sheetfeeder provided with two sheet hoppers (hereinafter, referred to as a"dual hopper automatic sheet feeder") typical of conventional automaticsheet feeders provided with a plurality of sheet hoppers. A printertransmits a sheet hopper select signal 51 to the automatic sheet feederfor selecting either sheet hopper. A sheet delivery signal 52 commandsthe operation of a delivery roller, namely, a signal to drive a steppingmotor provided in the automatic sheet feeder. Upon the reception of thesheet delivery signal 52, the automatic sheet feeder selects that sheethopper corresponding to the hopper select signal 51, and drives thestepping motor to rotate the delivery roller for feeding a sheet fromthe selected sheet hopper to the printer.

Upon the detection of the sheet by a detector, not shown, the printertransmits a signal to the automatic sheet feeder to stop the sheetfeeding operation, and then the automatic sheet feeder stops thestepping motor, thus stopping the sheet feeding operation. Indicated at53 is a graph or line representing the sheet feeding speed of theautomatic sheet feeder.

When a sheet feed command is given in a situation where the hopperselect signal is not transmitted properly from the printer to theautomatic sheet feeder, the sheet hopper specified previously and storedin the automatic sheet feeder is selected when the sheet feed command isgiven immediately after the automatic sheet feeder has been connected toa power source or the sheet hopper selected by the preceding hopperselect command becomes active when the sheet feed command is givenduring operation.

This control method, however, requires one signal line for transmittingthe hopper select signal 51 for selecting either sheet hopper, andanother signal line for transmitting the sheet delivery signal 52requesting feeding of a sheet. Once a host computer for controlling theprinter has given a command for an initial resetting, the printer isunable to send a new hopper select signal to the automatic sheet feederand, in some cases, the automatic sheet feeder selects the wrong sheethopper.

SUMMARY OF THE INVENTION

The present invention provides a method of controlling a dual hopperautomatic sheet feeder, whereby it is possible to solve problemsresulting from the use of one signal line for sheet hopper selection andanother signal line for starting sheet feeding, and wherein control of asheet feeding operation is achieved by using a single signal line.

The method of the present invention for controlling an automatic sheetfeeder provided with a plurality of sheet hoppers which are usedselectively to feed sheets to a printer provides that a hopper selectsignal and a sheet deliver signal are transmitted through a singlesignal line from the printer to the automatic sheet feeder. The pulsewidth of the hopper select signal is smaller than that of the sheetdelivery signal. The hopper select signal having a smaller pulse widthis transmitted to the automatic sheet feeder to select the sheet hoppercorresponding to the number of pulses of the hopper select signal. Astepping motor is driven to feed a sheet when the sheet delivery signalis transmitted to the automatic sheet feeder after the sheet hopper hasbeen selected.

Since the sheet hopper can be selected and sheet feed operation can bestarted by signals transmitted through a single signal line, the cost ofthe control system is reduced and the automatic sheet feeder itself willbe less expensive.

Furthermore, in executing an initial setting in response to a commandgiven by a host computer for controlling the printer after the hopperselect signal has been supplied to the automatic sheet feeder, the sheetdelivery signal can be canceled by transmitting a hopper select signalfor selecting a new sheet hopper from the printer to the automatic sheetfeeder. Hence, an incorrect selection of a sheet hopper is obviated andcorrect operation can be expected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an automatic sheet feeder embodying thepresent invention;

FIG. 2 is a sectional view of the automatic sheet feeder of the presentinvention;

FIG. 3 is a block diagram of the automatic sheet feeder of the presentinvention;

FIG. 4 is a time chart of assistance in explaining a method ofcontrolling the automatic sheet feeder of the present invention;

FIG. 5 is a flow chart of a method of controlling the automatic sheetfeeder of the present invention; and

FIG. 6 is a time chart of assistance in explaining a conventional methodof controlling an automatic sheet feeder.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 are a perspective view and a sectional view, respectively,of an automatic sheet feeder embodying the present invention. Referringto FIGS. 1 and 2, indicated at 1 are connecting lugs for connecting theautomatic sheet feeder to a printer, at 2 is a sheet hopper for holdinga stack of sheets for printing, and at 3 is another sheet hopper similarto the sheet hopper 2. The sheet hoppers 2 and 3 may hold the same typesor different types of sheets.

The sheet hoppers 2 and 3 are provided with respective delivery rollers6 and 7 for feeding respective sheets 4 and 5 held therein one sheet ata time. The delivery rollers 6 and 7 are interlocked through a one-wayclutch, not shown, with a stepping motor. Either of the delivery rollers6 or 7, depending on the direction of rotation of the stepping motor, isdriven.

The sheet 4 or 5 delivered from the sheet hopper 2 or 3 in response to acontrol signal given by the printer is held between a platen 8 andclamping rollers 9 and 10 pressed toward the platen 8 and is fed as theplaten 8 rotates. A print head 11 strikes, through an ink ribbon, thesheet 4 or 5 pressed against the platen 8, thereby achieving printing.Then, the sheet 4 or 5 is delivered by rollers 12 and 13 that arepressed toward each other to a stacker 14.

Rollers 15 and 16 or rollers 17 and 18 operate in synchronism with therotation of the plate g and are provided to deliver the sheet 4 or 5delivered by the delivery roller 6 or 7 to the platen g in synchronismwith the operation of the print head 11. The automatic sheet feeder alsois provided with a hand feed slit 19 for manual sheet feed.

FIG. 3 is a block diagram of the automatic sheet feeder of the presentinvention. Referring to FIG. 3, a control unit 21 of the printer isconnected to a control circuit 23 in the form of a one-chipmicrocontroller of the automatic sheet feeder by an interface signalline 22. The control circuit 23 comprises a CPU 24, a ROM 25 storingprograms, a RAM 26 for storing data and results of intermediatecalculations, an I/O port 27 for exchanging therethrough control signalswith the printer, and an I/O port 28 for exchanging therethrough controlsignals with a stepping motor driving circuit 29. The stepping motordriving circuit 29 drives a stepping motor 30 for driving the deliveryroller 6 and 7 to deliver the sheets one by one from the sheet hoppers 2and 3.

A method of controlling the automatic sheet feeder of the presentinvention will be described hereinafter with reference to a time chartshown in FIG. 4 and a flow chart shown in FIG. 5.

Referring to FIG. 4, indicated at 31 is a control signal from theprinter to the automatic sheet feeder, and 32 is a graphicalrepresentation of the speed at which the sheets 4 or 5 are delivered. T₁and T₂ are pulses of the control signal 31 from the printer to theautomatic sheet feeder for sheet hopper selection. A pulse T₄ in thecontrol signal 31 from the printer to the automatic sheet feedercommands the automatic sheet feeder to deliver the sheets 4 or 5. On thegraph 32, T₃ is a delay time by which the actuation of the steppingmotor 30 is delayed from a moment when the automatic sheet feederreceives a control signal, i.e. pulse T₄, commanding the delivery of asheet 4 or 5.

Upon the reception of the control signal 31 and print data from the hostcomputer, the printer transmits the pulses T₁ and T₂ to the automaticsheet feeder before transmitting a pulse T₄ to the automatic sheetfeeder to deliver the sheet 4 or 5. The pulses T₁ and T₂ need have onlythe least sufficient widths necessary for sheet hopper selection and arefar shorter than the delay time T₃.

One of the sheet hoppers a (for example, the sheet hopper 2 in FIG. 1)and b (for example, the sheet hopper 3 in FIG. 1), for example, thesheet hopper a, is selected when only the pulse T₁ is applied to theautomatic sheet feeder, and the other sheet hopper b is selected whenboth the pulses T₁ and T₂ are applied to the automatic sheet feeder.

If the pulse T₄ requesting delivery of a sheet is applied to theautomatic sheet feeder before applying thereto either pulse T₁ or thepulses T₁ and T₂, the automatic sheet feeder delivers the sheet held bythe sheet hopper selected by the preceding hopper select command, or theautomatic sheet feeder delivers either the sheet 4 held by the sheethopper a or the sheet 5 held by the sheet hopper b, specified beforehandas an initial instruction.

The operation of the automatic sheet feeder of the present inventionwill be described with reference to the flow chart shown in FIG. 5.

Step 1: The CPU 24 selects the sheet hopper a as a default.

Step 2: The automatic sheet feeder stands waiting for control signals.

Step 3: The automatic sheet feeder measures the pulse width of the pulseT₁ upon the reception of the pulse T₁ from the printer.

Step 4: The CPU 24 makes a query to see if the pulse width of the pulseT₁ is not longer than the delay time T₃. Step 5 is executed when theresponse is affirmative or the program jumps to Step 12 when theresponse is negative.

Step 5: The sheet hopper a is selected. (The default is maintained.)

Step 6: The automatic sheet feeder stands waiting for the reception ofthe pulse T₂ through the signal line 22.

Step 7: The pulse width of the pulse T₂ is measured.

Step 8: The CPU 24 makes a query to see if the pulse width of the pulseT₂ is not longer than delay time T₃. Step 9 is executed when theresponse is affirmative or the program jumps to Step 12 when theresponse is negative.

Step 9: The sheet hopper b is selected.

Step 10: The automatic sheet feeder stands waiting for the reception ofthe pulse T₄ through the signal line 22 from the printer.

Step 11: The automatic sheet feeder remains inoperative for the delaytime T₃ after the reception of the pulse T₄.

Step 12: The delivery roller of the selected sheet hopper is actuated tostart feeding a sheet.

Step 13: The stepping motor 30 is driven according to a predeterminedprofile of rotating speed during the duration of the pulse T₄.

Step 14: The stepping motor 30 is stopped at the end of the pulse T₄ tostop the delivery roller.

The sheet drawn out from the sheet hopper by the delivery roller 6 (or7) is delivered to the platen 8 by the rollers 15 and 16 (or 17 and 18)rotating in synchronism with the platen 8. Then, the print head 11prints on the sheet. The sheet is delivered to the stacker 14 after thecompletion of printing on the sheet.

The present invention is not limited in its application to the foregoingembodiment, but various modifications are possible. The invention may bepracticed otherwise than as specifically described above withoutdeparting from the spirit and scope of the invention.

For example, the present invention is applicable to controlling anautomatic sheet feeder provided with three or more sheet hoppers. Whenthe automatic sheet feeder is provided with a plurality of sheethoppers, respective pulse signals each having a number of pulsesrepresenting each sheet hopper are used, and the selected sheet hopperis identified by the number of pulses included in the pulse signal.

As is apparent from the foregoing description, a method of controllingan automatic sheet feeder in accordance with the present invention usesa single signal line for selecting of a sheet hopper and for initiatingthe delivery of a sheet. Accordingly, the method of the inventioncurtails the number of signal lines of the system, simplifies thecontrol of signals, and hence enables the use of an inexpensiveautomatic sheet feeder.

We claim:
 1. A method of controlling an automatic sheet feeder providedwith a plurality of sheet hoppers containing sheets, wherein sheets fromselected of said sheet hoppers are to be delivered to a printer, saidmethod comprising:transmitting through a single signal line from saidprinter to said automatic sheet feeder a control signal including ahopper select signal for selecting a respective said sheet hopper and asheet delivery signal for delivering a sheet from a selected said sheethopper; providing said hopper select signal in the form of one or morepulses and said sheet delivery signal in the form of a pulse having apulse width greater than the pulse width of said pulse or pulses of saidhopper select signal; and identifying each said sheet hopper by arespective number of said pulses of said hopper select signal.
 2. Amethod as claimed in claim 1, wherein said automatic sheet feederreceives said control signal as said hopper select signal when the pulsewidth of said pulse or pulses from said control signal is less than apredetermined time.
 3. A method as claimed in claim 2, wherein saidautomatic sheet feeder receives said control signal as said sheetdelivery signal when the pulse width of the pulse or pulses from saidcontrol signal is greater than said predetermined time.
 4. A method asclaimed in claim 3, comprising commencing delivery of a sheet from theselected sheet hopper after a delay corresponding to said predeterminedtime from the reception by said automatic sheet feeder of said sheetdelivery signal.
 5. A method as claimed in claim 3, comprisingcommencing delivery of a sheet from the selected sheet hopper after adelay corresponding to said predetermined time from the reception bysaid automatic sheet feeder of said sheet delivery signal.
 6. A methodas claimed in claim 1, comprising transmitting said hopper select signalto said automatic sheet feeder before transmitting said sheet deliverysignal.
 7. A method as claimed in claim 1, wherein said automatic sheetfeeder receives said control signal as said sheet delivery signal whenthe pulse width of the pulse or pulses from said control signal isgreater than a predetermined time.